1. Field of the Invention
The present invention relates generally to imaging financial documents. More particularly, the present invention relates to the use of a charge coupled device and a compensation reference to compensate for intensity variations during document imaging.
2. Background
In the banking industry, many interrelated functions must be performed on a daily basis and in an effective manner. For example, checks and deposit slips are commonly processed at extremely high rates. To further complicate matters, the processing of these documents must also be coordinated between institutions. Computerized document processing systems have therefore evolved over the years to assist in handling high throughput and increasing feature set.
Imaging is an important aspect of document processing systems with respect to financial institutions. For example, digital customer identification can often be critical and is relied upon heavily for transactions involving high dollar amounts. As a result, signature cards are commonplace and photographic identification is becoming increasingly popular with the advancement of digital signal processing. Check imaging is also very important. Image-enabled document processors with camera illumination systems are therefore a part of everyday banking functions. In fact, virtually every FDIC institution employs some type of camera illumination system for imaging and digitizing information contained on checks and other financial documents.
Imaging systems typically use a light source, such as a circuit board with an array of LEDS, to illuminate the subject. The source illumination is reflected back from the subject and harnessed by an optical system having lenses and mirrors. The intensity of the reflected illumination is used to control the illumination level of the final image. Light sources such as LEDS, however, are susceptible to aging and changes due to heat. Aging and heat in turn affects illumination intensity. The result is a variation in illumination intensity for the same control settings. For example, as ambient temperature increases, the relative intensity of an LED will decrease for the same LED current level. Recognizing this, conventional systems attempt to compensate for intensity variations due to heat and age. One approach is to use a photo-sensor to measure the intensity of light reflected from the subject. This information is then passed on to a host processor which calculates adjusted control data based on the measured intensity. A charge coupled device (CCD) also detects the reflected illumination and is used by the host processor in conjunction with the photo-sensor to produce the final image with the appropriate illumination level. A difficulty associated with using a photo-sensor to gage the illumination intensity of the light source is the possibility of errors due to variability in parts, alignment and sensitivity tolerances. It is therefore desirable to reduce the error associated with compensating for variations in illumination intensity. It is also desirable to reduce the number of parts and manufacturing steps associated with such compensation.
Other approaches use fixed time intervals or a temperature sensor, such as a thermistor, to determine intensity variation. Under such approaches, an indirect approximation can be made on the basis of a known age and temperature. These approaches, however, are subject to the same difficulties noted above. Approximating illumination intensity further increases the potential for error and adds overall processing costs to the system.
In a first aspect of the invention, an imaging system for an image-enabled document processor includes an illumination system, a CCD system, and a host processor. The illumination system provides reflected illumination, and the CCD system directly detects the reflected illumination from the illumination system. The CCD system further converts the reflected illumination into illumination data. The host processor converts the illumination data from the CCD system into image data and adjusted control data, wherein the adjusted control data sets the new illumination drive control.
In a second aspect of the invention, a computerized method for imaging a document includes the step of generating an illumination profile for an imaging system. Adjusted control data is then generated for the imaging system based on the illumination profile and a reference illumination intensity. The method further provides for imaging the document with the adjusted control data.
In a third aspect of the invention, a computerized method for generating adjusted control data for an imaging system based on an illumination profile and a reference illumination intensity is provided. Reference control data is generated, and a reference illumination intensity is directly measured with a CCD. The method further provides for calculating the adjusted control data.